Rigify generated rig, hand IK controller has unexpected rotation
Solved with the help of CGDive! https://blender.stackexchange.com/users/25308/cgdive 
The generated rig tries to correct the roll automatically by default, but this can be overwritten by selecting each upper_arm bone and in Bone Properties &gt; Rigify Type &gt; Rotation Axis selecting the rotation axis manually. If you have copied the roll orientations from the human metarig template, then this should be Z manual for the arms. This causes the hand IK control to be correctly oriented when generating the rig.